Certified Rhythm Analysis Technician (CRAT) Practice Exam

A "failure to capture" occurs when the pacemaker sends an electrical impulse, but the heart does not respond by contracting. This situation typically arises because the electrical impulse does not effectively stimulate the cardiac muscle, which can happen for various reasons including lead dislodgment, poor lead placement, or high thresholds for myocardial stimulation.

When the pacemaker fires yet there is no resultant mechanical contraction of the heart, it indicates that the electrical signal is not successfully translating into a cardiac action potential, and thus does not lead to effective heartbeats. This scenario is critical to recognize because it directly impacts the patient's cardiac output and overall hemodynamics. Understanding this concept is essential for effective monitoring and troubleshooting in patients with pacemakers.

In contrast, the other options describe different issues that relate to pacemaker function but are not specifically about a "failure to capture." For instance, a ventricular lead not sensing a QRS complex pertains to sensing issues but does not affect the capture directly. Similarly, an atrial lead detecting non-cardiac signals and QRS complexes occurring without proper pacing relate to sensing discrepancies and timing, rather than the defined concept of failing to capture the heart's activity.